1. Field of the Invention
The present invention relates to a technology that can be employed in an image processing machine such as color copier, which is designed to scan an original document or paper and print a duplicate image on a recording sheet, for preventing the forgery and counterfeiting of paper currency or other monetary instruments.
2. Description of the Related Art
With the spread of advanced digital color copying technology and copying machines incorporating such technology, the forgery and production of counterfeit paper currency, stock certificates, bearer bonds, and other monetary instruments has become a problem. In order to prevent such forgery, image processing devices equipped with anti-counterfeiting capability have been developed. Such devices contain pre-stored image data representing images of items for which copying is prohibited. When a user attempts to copy an original item, the image data that is scanned-in is compared against the pre-stored image data using pattern-matching techniques, and when the scanned image data matches the pre-stored image data, image formation on the copying sheet is prohibited. Alternatively, copying may be prohibited by having an entirely black image printed out onto the copy sheet.
One problem with such conventional systems, however, is that a large amount of memory is required to store the images of the various forms of currency and certificates in order to prevent them from being copied. Additionally, accounting for possible slanting or awkward angles of the original material in the scanned image data makes the comparison procedure performed by the image processing device very complicated.
It is thus an object of the present invention to provide an image processing device and method which determine whether or not items being copied are copy-prohibited items based on a histogram of the brightness levels of the copy-prohibited image and/or based on the size (area) of the copy-prohibited image as calculated from said histogram, thereby requiring less memory and a simpler procedure in determining whether or not scanned items are copy-prohibited.
In order to accomplish this object, according to one aspect of the present invention, an image processing apparatus includes a scanning unit for scanning an original item, a histogram generating unit for generating a first histogram of signal (first color histogram) from image signals scanned in by the scanning unit, and a copy-prohibited determining unit for determining based on the first histogram whether or not the item being copied is copy-prohibited. With such an image processing apparatus, the process for determining whether or not copying should be prohibited is simplified.
The copy-prohibited determining unit may include an area calculating unit for calculating the area (first area of the scanned original item based on the first histogram, a storage unit for pre-storing RGB signal histograms (a group of second histograms of copy-prohibited materials such as paper currency, stock certificates, bearer bonds and the like and the sizes (a group of second areas of these copy-prohibited materials, and a comparing unit for comparing each of the second histograms together with the size of the corresponding copy-prohibited material with the first histogram together with the size of the scanned item.
The copy-prohibited determining unit may determine that copying should be prohibited when both the first histogram and first area match any of the second histograms and the size of the corresponding copy-prohibited material. With such a copy-prohibited determining unit, the determination of whether or not copying should be prohibited can be made precisely.